Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

People who are happy, lively, calm or exhibit other positive emotions are less likely to catch colds and report fewer symptoms of the illness when they are under the weather.

The new finding held true regardless of personality traits such as optimism, extraversion and self-esteem. A person’s age, race, gender, education and body mass also did not make a difference.

Researchers interviewed 193 volunteers, aged 21 to 55, over several weeks to assess their moods and overall emotional states, and then infected them with either a rhinovirus, known to cause the common cold, or an influenza virus, responsible for the basic flu.

The volunteers were then quarantined to see if they came down with a cold or the flu. While the study found happiness is associated with boosted health, it suggests the opposite might not be true.

People who reported more negative emotions, such as depression, anxiety and anger, were not any more likely to catch colds than normal controls, the study found.

The study, led by psychologist Stephen Cohen of Carnegie Mellon University, will be detailed online in the journal Psychosomatic Medicine.